Centaur Carbon Filter ?'s

Newbie here with some questions about a 2 cubic foot Centaur carbon filter I am setting up. It will be used to capture the iron precipitated out of the well water by a hydrogen peroxide injection. It has a 12x48 tank and a Clack WS1 valve that was previously on a water softener. Is the 12x48 tank large enough to hold 2cf of carbon and backwash properly? Doing research, some sites say that the backwash rate of the carbon should be 8-10gpm per square foot of media. I am assuming that with the roughly 7.8sq ft of this tank that if using the higher backflow rate of 10gpm then the clack valve would need an 7.5 gpm dlfc button, is this correct? Another concern is the type of underbedding needed. I have a old 16lb bag of #8 garnet here, is this okay to use under the carbon?

The house that this filter is being used on has 3 bathrooms all with single head showers, no tubs, a washer, no dishwasher and there are two senior occupants. 99% of the time there are only two people living in the house, but up to 6 guests can use the house two or three times for up to a week at a time per year. I have only seen all three showers being run at once maybe a half a dozen times in the past 20 years. I figure a high water usage rate of around 9gpm with 3 showers going and can't really see all three showers and the washer running at the same time, but maybe the kitchen sink might get used for a glass of water or to wash dishes, but again it would be extremely rare to have all of these happening at the same time. Is 2 cu ft of Centaur carbon enough for 9gpm flow rate? Is one normal 14 minute backwash setting sufficient for this filter? How often should the backwash occur?

Just FYI: The water supply has tested for 4ppm of ferrous iron, a PH of 7.3, TDS of 300, 9 grains of hardness, Manganese-Copper-Nitrites-Sulfides-Tannins-Iron Bacteria, nor Coliform were detected.

I sure do appreciate any and all help you experts can offer. Most of the water treatment people where the house is located seem to be more interested in selling product that up to this date hasn't worked properly. I would much rather learn all I need to know from someone who knows what they are talking about and get the water iron free and then maintain the system then to rely on a few local water treatment shops.

Gary has been pushing the Clack valve for years as a DIY's dream and it was Dittohead's video on the rebuilding of the Clack valve that sold me on this valve. His video on the Fleck 7000 rebuilding was awesome too, but I really liked the idea of there being no screws on the WS1.

A 12x48 is rated for 1.7 Cu. Ft. of media with a 50% freeboard (50% of the media height, not 50% of the tank). Assuming you fill the bottom dome (Domes are not considered in tank media quantities).

GAC is usually backwashed at 10 GPM per Sq. Ft. 6" x 6" x3.14 / 144 x 10 = 7.85 GPM, you should use a 7-8 GPM flow control on the Clack valve.

Garnet is an excellent underbedding for GAC, just be sure it completely covers the bottom screen. Properly, it should fill the dome, but I doubt 16 pounds will do that. The Dome on a 12" tank is .13 Cu. ft. it will barely cover the bottom screen depending on what type of screen you have. #8 Garnet is approximately 150# per Cu. Ft.

Backwash frequency depends on the water use, but considering the high level of iron, I would assume weekly or every other week should be sufficient.

As to the Clack or 7000, both are excellent, and both should last 5-15 years between rebuilds. If you are using a water softener valve for the clack, be sure to plug the brine, and remove the brine piston from inside the valve. Not critical, but proper.

How are you injecting your chemical?

I am doing the 5800SXT rebuild next, I also am redoing the 7000 with some cut-away views.

Thank you for your help! I will load the mineral tank with 1.7 Cu. Ft. of carbon and get some more garnet to fill the bottom dome. The bottom screen on the riser tube almost looks like a bunch of stacked plates with fine slots all around it and is approximately 3" or so tall. The brine piston removal was very easy using your excellent video as a guide and also using the clack manual to tighten up the drive cap assembly correctly. I am planning on using a Chemilizer pump to inject the peroxide. The house is on a shared well and will need a proportional rate pump and this looked like one of the best ways to get it without having to buy an electric injection pump, control module and flow meter. Hopefully it will work out as well as expected. Would you know what residual of peroxide that would be the best to shoot for before the water enters the carbon filter? It would seem to make sense to end up with as little H202 as possible after it oxidizes the rust, but I don't know if that is true.

I look forward to your 5800 valve rebuild video and the cut-away views of the 7000 valve as well. I never knew that water treatment was so complex, but yet interesting at the same time.

One last off the topic question. How much iron can a 1/3 cu. ft. of KDF-85 media remove by itself in a backwashing filter? I haven't had any luck finding that answer in my research on the stuff.

The 12x48 is fine. No need to get a 12x52. Even a 12x52 is only rated for 1.8 Cu. Ft., but most companies use it for 2 Cu. Ft. I would recommend household bleach injection. It requires a lower dosage than hydrogen peroxide, is readily available, and is highly stable in solution. Some people will say that the holding tank needs to be cleaned and the liquid solution changed regularly, in commercial applications this is true, for residential, just check the bottom of the tank for precipitates, clean as needed. Let the tank run almost dry prior to cleaning. Cleaning is nothing more than rinsing the tank out for a minute, not exactly difficult. The HN55 is one of my favorite designs, simple, accurate, inexpensive, and durable. It is a bit noisy so dont mount it to the wall behind your bedroom.

As to the KDF85 question, it does a fairly good job as a non chemical iron filter, similar to pyrolox. Using this media for a whole house iron filter is an excellent idea, but should only be done after proper pilot testing, or by the dealers who are well versed in their regions water and the medias capability for that water. This is the same with most non chemical iron removal systems. When in doubt, chlorine injection, contact tank, GAC is always a safe way to go.

If you look a bit further on that same site you will find they sell hydrogen peroxide injection systems with the Stenner pump. They also make no mention of injecting hydrogen peroxide with the Chemilizer.

As I understand it the issue is that hydrogen peroxide has a tendency to outgas and that causes problems for diaphram and positive displacement pumps in maintaining prime.

I will get a 12' x 52" tank if you think it is necessary. I just had the 12" x 48" tank on hand and thought it would do the job. Thanks for your help! John

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I forgot you already had the tank but, a 12 x 52 has an additional 4" and that means all 2.0 cuft and the underbed fits in the tank.

BTW, I do not like peroxide or solution feeders but chlorine bleach is much better, less expensive and much easier to handle, find and store.

Solution feeders can be a PIA to get to work consistently. The solution weakens in the tank and the solution will separate causing the stronger solution to be in the bottom of the solution tank where the pick up is. That is caused because bleach is heavier than water and will separate and fall to the bottom of the tank if not stirred constantly. Then each chlorine injection is weaker than the previous and maintaining the residual can be difficult. So you increase the volume of the solution and when you add more solution, you decrease the volume.

I think a much better way to use chlorine is with an erosion dry pellet chlorinator and special mixing/retention tank that is equivalent to a regular 120 gal retention tank and allows draining sediment out the bottom followed by the carbon filter. I sold hundreds of them since the early 1990s and they work every time with little to no babysitting.

"The HN55 is one of my favorite designs, simple, accurate, inexpensive, and durable. It is a bit noisy so dont mount it to the wall behind your bedroom." LOL! It might attract wood peckers with its clicking sound if mounted there! Thanks for the info on the KDF media, it sounds like an interesting media. Does it need the same 15% dissolved oxygen that birm, and filox need to work well? Thanks again for your help!

BTW, I do not like peroxide or solution feeders but chlorine bleach is much better, less expensive and much easier to handle, find and store.

Solution feeders can be a PIA to get to work consistently. The solution weakens in the tank and the solution will separate causing the stronger solution to be in the bottom of the solution tank where the pick up is. That is caused because bleach is heavier than water and will separate and fall to the bottom of the tank if not stirred constantly. Then each chlorine injection is weaker than the previous and maintaining the residual can be difficult. So you increase the volume of the solution and when you add more solution, you decrease the volume.

I think a much better way to use chlorine is with an erosion dry pellet chlorinator and special mixing/retention tank that is equivalent to a regular 120 gal retention tank and allows draining sediment out the bottom followed by the carbon filter. I sold hundreds of them since the early 1990s and they work every time with little to no babysitting.

I wonder if someone makes a small pump or mixer that could be used to recirculate the bleach or peroxide mixture in the solution tank that would help alleviate the stratification of the water/chemical mix? Time for more research! ;-) I like the idea of the pellet chlorinator, but since my Dad will be the one having to maintain the system most of the time I don't believe that he would like to have to use muratic acid to clean out parts of the feeder every couple of months. He has very bad arthritis in his hands and I think a bleach or peroxide system would be easier for him to keep up when I am not around. I appreciate all of the advice you have given me!

Not everyone has to use any acid to clean the center tube and if he had to, white vinegar works and he can soak it for weeks if needed because he gets two center tubes, one to be used and a spare to be cleaned between having to add new pellets. That's usually 2-3 months and depends on how much water is used. Once a month or when he adds pellets he opens a ball valve on the bottom of the mixing tank and flushes any dirt out of the mixing tank until it runs clean. That drain he'd connect a piece of a garden hose to and run the water to a floor drain or wherever he had to. He could leave the hose connected and simply coil it up.

As to the KDF needing at least 15% of the amount of iron to dissolved oxygen, most oxidation medias need that amount. Why would you chose Hydrogen peroxide over Chlorine?

As to the solids in Chlorine solution tanks... it is usually not a problem, and typically only need annual cleaning. Most service companies leave the bottom screen a few inches off the bottom to lengthen the time between tank cleanings. The amount of oxidative loss is minimal in a month for this system. The pellet systems work fairly well, not my preferance but we do sell a lot of them. Mainly to the "low budget" companies. The pellet feeders are very cheap and as long as you dont let it run out and constantly clean them, they work. They do tend to overchlorinate, but this is not an issue, Carbon will not last as long as it will with a proper chlorine feed, but we are talking a few years between carbon changeouts. Check out this pump as well, a few bucks more, extremely high quality. http://www.dultmeier.com/products/search/10686

I haven't heard anyone but you mention solids build up in solution feeder tanks so I'm not sure why you keep mentioning it. Raising an injection pump's pickup tube a few inches off the bottom of the solution tank allows the stronger solution on the bottom to not be used and to weaken over time. I think that would lead to your solids build up problem.

Chlorine is corrosive and I thought hydrogen peroxide would be less so. From what I have read about hydrogen peroxide I get a good feeling about using it over chlorine. Whether that is a sane thing I do not know. I will check out the dultmeier pump to see what that one is like.

Not everyone has to use any acid to clean the center tube and if he had to, white vinegar works and he can soak it for weeks if needed because he gets two center tubes, one to be used and a spare to be cleaned between having to add new pellets. That's usually 2-3 months and depends on how much water is used. Once a month or when he adds pellets he opens a ball valve on the bottom of the mixing tank and flushes any dirt out of the mixing tank until it runs clean. That drain he'd connect a piece of a garden hose to and run the water to a floor drain or wherever he had to. He could leave the hose connected and simply coil it up.

You're welcome.

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How often on average does the feeder vessel need to be removed and cleaned out? Is it usually once a year? Can my dad leave his home for a couple of weeks or a month without having to remove the pellets from this system? Cleaning the tubes with vinegar is something that he probably wouldn't mind doing and flushing the mixing/retention tank is something he will have to do no matter which of these systems we decide on.

Another consideration in chosing between injection and a pellet feeder is the continuing cost of operation. Chlorine from pellets costs about 10 times as much as from household bleach--$150 per year compared to $15.

If you are willing to accept the issues with chlorine introduced prior to the pressure tank then with injection it can be done with out purchasing a large solution tank and diluting the chlorine solution because household bleach is 5-6% solution as sold and this can be used with a properly sized Stenner adjustable injection pump for direct injection. Using a smaller container and undiluted bleach solution for injection virtually eliminates problems with solution stratification and changes in solution strength--but at the cost of more frequent solution refill.

Chlorine is corrosive and I thought hydrogen peroxide would be less so. From what I have read about hydrogen peroxide I get a good feeling about using it over chlorine. Whether that is a sane thing I do not know. I will check out the dultmeier pump to see what that one is like.

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Both chlorine and hydrogen peroxide are strong oxidizers.

The really significant difference in water treatment is that the products of oxidation with hydrogen peroxide are benign while chlorine can produce some nasty compounds.